The present invention is directed to an improved 
electroplating method, 
chemistry, and apparatus for selectively depositing 
tin / lead solder bumps and other structures at a high 
deposition rate pursuant to manufacturing a microelectronic device from a workpiece, such as a 
semiconductor wafer. An apparatus for plating solder on a microelectronic workpiece in accordance with one aspect of the present invention comprises a reactor chamber containing an 
electroplating solution having free ions of 
tin and lead for plating onto the workpiece. A chemical 
delivery system is used to deliver the 
electroplating solution to the reactor chamber at a high flow rate. A workpiece support is used that includes a contact 
assembly for providing electroplating power to a surface at a side of the workpiece that is to be plated. The contact contacts the workpiece at a large plurality of discrete contact points that isolated from 
exposure to the electroplating solution. An 
anode, preferably a consumable 
anode, is spaced from the workpiece support within the 
reaction chamber and is in contact with the electroplating solution. In accordance with one embodiment the electroplating solution comprises a concentration of a 
lead compound, a concentration of a 
tin compound, water and 
methane sulfonic acid.